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Thread: TBI 7747 Idle Fueling Issue while Cold - Too lean, AFRs not responding to bin changes

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  1. #8
    Carb and Points!
    Join Date
    Aug 2014
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    Detroit Suburbs
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    9
    Another handful of changes and what seems to be more progress (at least around 9 deg C).

    Painting with a bit of a broad brush, I decided to disable most temp based corrections an allow the Open Loop AFR vs Temp to handle most of the work.

    This seemed to help with cold startup behavior, specifically the act of putting the vehicle in gear very quickly after startup. No stall this time.

    A bit more driving found another hole in my AE tables. I had flatlined all of the AE correction vs CTS to the highest value in the table (0.398). Now at 85C, the upshifts went a bit leaner than before, not initially, but at the end/slightly after the shift. I dropped the MAP - Filter vs Coolant table down to .2 across the board, which seemed to help.

    One more AE finding was on low RPM tip-in. It sputtered and bogged here some when warm. This was on small tip in events that were enough to trigger the AE, but not so much that a downshift would happen. I'm guessing here this is a small TPS AE (if any) coupled with a large MAP AE and it resulted in too much fuel. So, I dropped the MAP AE some, especially in the 0,20,49 cells. Tested this by holding the brake in drive/reverse then doing light throttle tip in events. With the prior cals, the WBO2 would peg rich. New cals go just slightly leaner (12:1 at idle), but not so much that is misfires. A little over-correction on the way back down (MAP AE possibly a bit high still for this condition), but live-able. Would be nice if these parameters had an RPM component to them to keep large AE PW adders from bogging the engine at low airflow conditions.

    Data log and latest bin attached (log is from a couple bins before changing the AE).
    Attached Files Attached Files

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